Terrain

The surrounding country is very hilly, but the immediate approaches are unobstructed being over the water of Port Nicholson from the north and Cook Straight from the south. As Cook Strait is a relatively narrow gap between the mountain ranges of the North and South Islands, winds are considerably reinforced orographically in the Wellington area and are channelled strongly in the north-north westerly and southerly directions.

There is also some local north-south channelling of the surface winds at the Airport owing to the hills parallel to and on either side of the runway rising to about 500ft in depth.

Weather

Wind

Wellington can experience rapidly changing weather conditions and strong winds.

Due to the funnelling effect of the break in the mountain chains between North and South islands, strong winds occur relatively frequently at Wellington Airport

Brief periods of very strong winds can occur with the passage of line squalls in strong southwesterly airstreams. The associated wind can sometimes gust to at least 50kt within a matter of seconds from near calm conditions. The period of strongest gusts usually persist for less than half and hour before the wind settles.

Turbulence

Moderate to severe turbulence occurs in most situations associated with strong northerly or southerly gradient winds becuase of the flow over the hilly terrain. However, turbulence alone is not usually sufficient in itself to restrict operations as the surface winds usually surpasses the limits for any particular aircraft before the turblulence becomes excessive. The principle exception to this rule is when the surface wind across Cook Strait is between 250º and 290º and greater than about 30kt. Under these conditions sheltering reduces the surface wind at Wellington Airport but there is a strong shear zone between 300ft to 1000ft often accompanied by severe turbulence.

Fog/Visibility

Fog is not common at Wellington Airport, being reported on average about 6 days per year. Typically forming as sea fog it can occur at anytime of the day or night. It is most common in January and March.

On rare occasions radiation fog may form over the Hutt Valley and be carried by light NE winds across the harbour to the airport, and its duration seldom exceeds one hour.

Heavy precipitation unaccompanied by low cloud or fog but sufficient to reduce visibility enough to restrict operations is rare.